This invention relates to a fixing apparatus that can typically be used in an image forming apparatus for the purpose of fixing a developing agent such as toner to the image forming medium.
Conventionally, a fixing apparatus for fixing the toner on an image forming medium is driven for warming up (a pre-run) prior to the fixing operation, in order to secure the ratio of fixing toner on the image forming medium to a required level. For warming up, the heater is turned on and the heat roller is driven to rotate. As a result, the heat roller and the press roller that is held in contact with the heat roller are warmed. The fixing ratio of fixing the developing agent to the image forming medium is secured to a required level by such a warming up operation.
The major objective of such a warming up operation is to secure the fixing ratio to a required level. The warming up time of the warming up operation that is performed for the entire apparatus is reduced as much as possible in fixing apparatuses that have been marketed in recent years. However, as the warming up time is reduced, the risk of producing a large curl on the sheet of paper coming out of the fixing apparatus rises. It is believed that the sheet of paper is curled by the fixing apparatus because the developing agent is fixed to the sheet of paper by applying both pressure and heat by means of the heat roller and the press roller.
As the extent of curl of the sheet of paper increases, so does the likelihood of it being jammed in the conveyance path after the fixing process, thus it may not be properly delivered onto the delivery tray. Other problems may also arise. Therefore, some conventional fixing apparatuses are provided with a mechanism specifically designed to physically reduce the risk of curling sheets of paper, and is arranged on the conveyance path of sheets of paper coming out of the fixing apparatus.